Passers-by are understood to have battled bravely to pull the pair out of their blazing car, which burst into flames after a two-car collision on the A47 at Wendling, near Dereham, at 2.35pm.

But their efforts were in vain, with the 76-year-old woman passenger dying at the scene and the male driver, 77, losing his fight for life four hours later at the Norfolk and Norwich University Hospital.

A 69-year-old woman who was driving the other car remains seriously ill in hospital with injuries including two broken legs, a broken right arm, broken pelvis and internal bleeding.

It is the latest of dozens of serious accidents in recent years, and comes a few weeks after the EDP launched a campaign to fully dual and make other safety improvements to the A47.

Mid Norfolk MP George Freeman said the “tragic” accident added to the “urgency” to improve the busy road.

He said: “This is tragic news, and I know that all our hearts will go out to the friends and families of those were have been killed and injured.

“This is especially tragic at Christmas, which is a time for family. It’s a stark reminder of the danger of our roads at this time of year, and especially of the urgency of the need for improvements to the A47.”

Jenny Lock, the owner of Greenbanks Hotel at Wendling, which is close to the crash scene, said it was a “very dangerous” stretch of road.

She said: “Someone came in in a state of shock to use our fire extinguisher. Three members of staff went out to try to help but it was far too dangerous for them,

“It is a very dangerous road and there are always accidents here. We are frequently hearing sirens going past and there have been several fatal accidents.”

She added: “It is such a tragedy to happen on Christmas Eve for all the families involved and it is something they will remember every Christmas forever.”

The incident happened between Little Fransham and Dereham, close to the Wendling turn off, when a grey Vauxhall Astra heading towards Norwich was in collision with a silver VW Polo travelling in the opposite direction.

The road remained closed, with diversions in place, for several hours while police, fire and ambulance crews heelped the victims. An air ambulance was also at the incident.

Firefighters from Swaffham and Dereham bought the car blazes under control by 3.15pm.

Both of the people in the Astra are thought to be from Leicester, with the injured woman is understood to be from Norwich.

For decades, the EDP has been making the case - along with many local organisations - for the A47 to be fully dualled and for other safety measures to be made.

The latest campaign is two pronged - emphasising safety and a potential multi-million pound boost to Norfolk’s economy over 20 years, including 10,000 jobs, a £390m annual economic boost and up to £800m of private investment.

In November, MPs, Norfolk County Council, the New Anglia Local Enterprise Partnership and other campaigners formed the A47 Alliance and launched a united drive, with the backing of the EDP, to convince the government of the overwhelming business case for the upgrade.

Earlier this month, hopes were raised when transport minister Stephen Hammond said the government would in 2013 seriously consider the case to fund improvements.

During a meeting with A47 campaigners, he raised the prospect that he would, in 2013, name the project as one that might be funded under a government road improvement scheme sometime soon after 2015.

The 14 improvement being pushed for by the A47 Alliance include dualling the Acle Straight, creating a third river crossing at Great Yarmouth, and building an East Winch/Middleton bypass in West Norfolk.